(i) Technical Field
The present invention relates to an image forming apparatus and a computer readable medium storing a program.
(ii) Related Art
Image forming apparatuses for electrophotographically forming an image, such as copiers and printers, have been available which are configured to transfer (first-transfer) a toner image formed on a photoconductor onto an intermediate transfer body and then transfer again (second-transfer) the toner image onto a recording medium such as printing paper, thereby forming an image on the recording medium.
Examples of a full-color image forming method in a configuration including an intermediate transfer body include the so-called four-cycle method in which toner images of respective color components such as yellow (Y), magenta (M), cyan (C), and black (K) components corresponding to the same full-color image are sequentially formed using a single image forming unit and in which the toner images of the respective color components are sequentially first-transferred onto the intermediate transfer body so that the toner images of the respective color components overlap one another on the intermediate transfer body.
The four-cycle image forming apparatuses have features in that, for example, the first transfer of toner images onto the intermediate transfer body is not affected by the material of the recording medium, and may therefore be suitable for the increased image quality of a full-color image to be formed.
In the formation of a full-color image using a four-cycle image forming apparatus, a reference mark (such as a reflective seal) on one end portion in the axial direction of a transfer belt serving as an intermediate transfer body is detected using a non-contact photosensor, and the detection of the reference mark may trigger start of writing in the image processing, leading to alignment of pixels between colors in the sub-scanning direction. This process is also known as the registration control.
Here, high-accuracy detection may be based on the stable attitude of the reference mark and the stable operating distance of the photosensor.